KIN 1223 Unit 5 Lecture 2 The Brain General structure Embryological development 3 regions of enlargement of the neural procedure tube Developed brain Forebrain o Cerebral hemispheres o Basal Nuclei o Diencephalon Thalamus Hypothalamus Brainstem o Midbrain o Hindbrain Pons Medulla Oblongata Cerebellum Meninges 3 layers of CT separated by spaces or potential spaces Protect brain spinal cord Epidural space in cord only above dura 1 Dura Mater tough outer layer a Sub dural space 2 Arachnoid Mater thin transparent middle layer a Subarachnoid space CSF circulates 3 Pia Mater Transparent inner layer 4 Ventricles Interconnected cavities Within cerebral hemispheres brain stem Continuous with central canal Allow continuous circulation of CSF o Cerebrospinal Fluid CSF Clear fluid similar to blood plasma More Vitamin C More Na Cl and H ions than blood plasma Less protein and fewer Ca2 and K ions pH of CSF effects breathing and cerebral blood flow Formed in choroid plexuses Specialized capillaries in the ventricle s roof o Surrounded by ependymal cells 1 layer Fluid from blood stream is filtered as it moves through ependymal cells Enters ventricles as CSF CSF constantly produced and reabsorbed 500 mL daily 100 160mL circulating cord Reabsorbed into blood through arachnoid villus o Project into blood filled dural sinuses Circulates through ventricles subarachnoid space covers brain o CSF circulation most produced in lateral ventricles some Interventricular foramen in 3rd 1 Lateral Ventricle 2 3 3rd ventricle 4 Cerebral aqueduct 5 4th ventricle 6 Central canal of cord a Circulates around cord 7 Enters sub arachnoid space a Through openings in roof of 4th ventricle Functions Hydraulic shock absorber Transportation system o Blood Brain Barrier Controlled by 1 Tight junctions a Seal endothelial cells of brain capillaries together i Become least permeable in body 2 Thick basement membrane basal lamina a Surrounds external surface of capillaries 3 Feet of astrocyte processes cling to capillaries Some materials can pass through barrier o Glucose o Fats o Fatty acids o Alcohol o O2 o CO2 Can t pass o Most drugs o Metabolic wastes o Small amino acids o Some toxins o Cerebral Hemispheres or Cerebrum Thin outer layer of gray matter o Cerebral cortex o 75 of all neuron cell bodies in CNS Inner region of white matter o Bundles of myelinated nerve fibers o Connect neuron bodies to other parts of CNS o 3 Functional groups of fibers 1 Commissural Fibers a Connect structures in each side or hemisphere i Brain or cord right and left sides b Examples i Gray commissure of cord ii Corpus Callosum right left sides of cerebrum iii Massa Intermedia right left sides of thalamus 2 Association Fibers a Connect areas within the same hemisphere b Long connect between lobes c Short connect adjacent gyri within same lobe 3 Projection Fibers a Connect cerebrum with lower structures i Internal Capsule Open V or boomerang shape b Tracts can be specially located o Lobes of cerebral hemispheres Correspond to cranial bones o Frontal o Parietal o Temporal o Occipital o Insular deep to lateral sulcus Surface of lobes o Gyri gyrus ridges or convolutions Separated by o Sulci sulcus grooves or depressions o Arranged in distinct patterns with specific names All mapped for function o Highly organized o Sensory and motor functions for opposite side of body Left Hemisphere 90 dominant for Language activities speech writing reading Analytical reasoning math science Right Hemisphere Non dominant Non verbal functions interpreting musical patterns or spatial relationships Imagination artistic skill o Cortex involved with consciousness Perception of sensations Voluntary motor control Higher mental processing memory logic judgment o Other regions have specific functions o Hemispheres and Lobes Mapped for function Occipital vision Frontal higher mental functions Pre central gyrus primary motor Post central gyrus sensory Extensive Cortex mapping Brodmann s areas o German neuro anatomist o 47 50 areas 200 more since Brodmann Primary Functional Organization Mapping of motor and sensory cortexes o Homunculis depicts results caricature of body proportioned to represent extent of innervation of specific body areas Inferior extremity most medial Superior extremity middle Superior or cranial most lateral o Size represents degree or representation 1 Motor a Primary motor Pre central gyrus Initiates voluntary skeletal muscles i ii Origin of Corticospinal tracts b Broca s Motor Speech Area 2 Sensory a Primary sensory Post central gyrus i Directs muscles of tongue throat and lips articulating words i Information from receptors in skin and proprioceptors b Visual Cortex c Auditory Cortex i Receives sensory input from retinas i Receive input from hearing receptors in ear d Smell Uncus Olfactory i Medial and deep in temporal lobe e Taste Gustatory area 3 Association a Primary association areas i Anterior portions of frontal lobes ii Lateral parietal temporal and occipital lobes iii Function 1 Analyze and interpret sensory experiences especially with memory reasoning verbalizing judgment emotional feelings 2 Communicate with motor cortex for proper response b Frontal lobes i Prefrontal areas ii Higher intellectual processes iii Concentration planning complex problem solving iv Anterior and inferior prefrontal areas control of emotional behavior c Parietal lobes i Meaning of sensory information ii Aid in understanding speech iii Choosing words to express thoughts and feelings iv Awareness of body parts from posterior regions of area d Temporal lobes i Toward posterior ends of lateral fissures ii Complex sensory experiences iii Needed to understand speech read printed words remember visual scenes and music iv Wernicke s Area speech area understanding written and spoken words e Occipital Lobe i Analyze visual patterns ii Combine vision w other senses f General interpretative area Intersection of Parietal Temporal Occipital i ii Complex thought processing Broca s Area